Training for running races, whether humans, horses or dogs, and for other racing sports such as speed skating and cross-country skiing, involves building both muscle strength and endurance. Using the example of a human, a person who wishes to run an event such as the 10,000 meter (6.2 miles) would train by running distances to increase endurance and strength. That person may also use weight training to further build leg strength. These exercises, however, will not improve the runner's speed to its highest level. In general, the runner who wants to increase his or her power (power=strength/time) does so preferably by both increasing strength and decreasing the time required to cover a given distance.
The only way to improve running speed is sprinting running as fast as possible. The runner who is training for speed usually runs a series of sprints (repetitions or "reps") designed to train his or her muscles to react faster and become more coordinated, to progressively enable him or her to reach higher maximum speed and power. Generally, in order to achieve this, the runner needs to find his or her own best form and pace. Unfortunately, due to the impact of the runner's feet hitting the ground with a force many times that person's weight, it is extremely difficult to maintain maximum speed for any length of time, as needed to accomplish the goal. The joints are jarred and the leg muscles, especially the quadriceps, are required repeatedly to effectively lift an enormous weight, resulting in early exhaustion and, often, injury. Also, it can take on the order of 10 to 15 minutes to recover from one rep, so that an intense power workout consumes a great deal of time with a relatively small amount of actual running. Thus, "teaching" the muscles to react faster is a long, frustrating and sometimes painful task that prevents many runners from achieving their potential speed.
Devices are available which will allow a runner to float or be suspended in a swimming pool while moving the legs in a running motion. Similar devices are available for training race horses where the horse is tethered so that it is centered in a pool where it swims in place. Each of these devices provides a training means by which the impact of running is avoided. It is difficult, however, to achieve actual running form when there is no ground from which to push off. Also, the water provides resistance which builds muscle strength but prevents rapid motion for speed training.
In spite of its disadvantages, "pool jogging" provides a means by which an injured runner can begin to train without the risk of re-injury due to the stress and shock of pounding the ground. By lightening the runner's relative weight, he or she can recuperate by gradually reconditioning the leg muscles around the injury which may have atrophied during non-use. It would be desirable to use a method similar to pool jogging to provide a means for controllably lightening a racer's weight in a similar manner while still permitting the racer to attain correct running or racing form.